Put 23 people into a room and there is a 50% chance that two of them will share a birthday. This has implications for the security of stored credentials and sets a fundamental limit on our ability to ensure the integrity of data.

In the 1940's Claude Shannon proved the existence of a cryptosystem that afforded perfect secrecy -- a cipher with no mathematical weaknesses. The recipe? A random key equal in length to the message that can be used only once. Leave it to the Soviets to re-use keys, a fatal mistake that did not go unnoticed by American cryptanalysts during the Cold War.

If an intruder gains access to your network, these are some of the methods they will employ to eavesdrop on and hijack communications. After demonstrating several examples, we discuss recommended defenses.

Upon establishing a man-in-the-middle on the LAN, the intruder attacks a variety of cleartext and encrypted communications. We demonstrate what this looks like from the intruder's perspective, and describe several techniques for getting around the encrypted protocols in common use today.